81751613 has 2 divisors, whose sum is σ = 81751614. Its totient is φ = 81751612.

The previous prime is 81751603. The next prime is 81751687. The reversal of 81751613 is 31615718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 65966884 + 15784729 = 8122^2 + 3973^2 .

It is a cyclic number.

It is not a de Polignac number, because 81751613 - 2¹⁰ = 81750589 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81751613.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81751603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40875806 + 40875807.

It is an arithmetic number, because the mean of its divisors is an integer number (40875807).

Almost surely, 2^81751613 is an apocalyptic number.

It is an amenable number.

81751613 is a deficient number, since it is larger than the sum of its proper divisors (1).

81751613 is an equidigital number, since it uses as much as digits as its factorization.

81751613 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5040, while the sum is 32.

The square root of 81751613 is about 9041.6598586764. The cubic root of 81751613 is about 434.0090412014.

The spelling of 81751613 in words is "eighty-one million, seven hundred fifty-one thousand, six hundred thirteen".